I'm a beginner who's had maybe 5-6 planing days on a Starboard Rio M. It comes with a 16"/41cm Drake fin and I'm looking to size up the fin. The Star-Board Rio tuning page recommends "Drake R13 Race NR 540" but they're hard to find on the web so I have a couple of questions...

1. Do they still make/sell these fins? In the USA?
2. What would be similar to a Drake R13 Race NR 540?
3. Is it true that I can use any Tuttle fin in a Deep Tuttle box?